Method for manufacturing a dye scavenging substrate

ABSTRACT

A method for manufacturing a dye scavenging substrate which comprises the steps of: (a) providing an absorbent substrate; (b) passing the substrate through a bath containing an alkaline solution of a dye scavenging compound selected from: (i) a N-trisubstituted ammonium-2-hydroxy-3-halopropyl compound having the general formula (I), or (ii) a salt of epoxy propyl ammonium having the general formula (II), or a combination thereof; (c) subjecting the substrate to a pressure of from about 0.04 MPa to about 0.40 MPa; (d) wrapping the substrate in a water impermeable material and rotating the substrate for a period of from about 12 hours to about 60 hours; (e) removing the water impermeable material and passing the substrate through a bath containing an acid solution; (f) subjecting the substrate to a pressure of from about 0.15 MPa to about 0.40 MPa; and (g) drying the substrate.

FIELD OF THE INVENTION

The present invention generally relates to a method for manufacturing adye scavenging substrate.

BACKGROUND OF THE INVENTION

It is well known that a typical mix of articles in a laundry wash willhave somewhat different colors, even if sorted into the so-called“white” and “colored” batches. Although fading of dyes is more prevalentfrom new, unlaundered, or heretofore infrequently laundered goods, evenarticles with considerable fastness to washing, or having a long historyof numerous previous launderings, may continue to bleed small amounts ofdyestuff or colorant into the bath or wash water. The well known, butaggravating and undesirable result of such fading is that at least partof the extraneous, free flowing dyestuff which has bled from itsoriginal material article may then be absorbed, adsorbed, reacted with,or otherwise physically deposited on or associated with other articlesin the same wash liquor, thus discoloring this latter item.

Attempts to solve this problem have included treating the dyes orcolorants so that they have a greater affinity for the dyed material.Attempts have also been made to eliminate dyestuffs discharged in thewash water. International PCT Patent Publication No. WO-A-97/48789discloses a method of controlling undesirable dye or colorant dischargedin wash water, comprising placing in the wash a dye scavenging substratewhich when added to the wash scavenges and absorbs extraneous dye.WO-A-97/48789 also discloses a method of manufacturing the dyescavenging substrate.

It is an object of the present invention to provide an alternativemethod for manufacturing a dye scavenging substrate.

It is a further object of the present invention to provide an improvedmethod for manufacturing a dye scavenging substrate, which methodresults in the dye scavenging substrate having improved dye scavengingcapabilities.

Furthermore, other desirable features and characteristics of the presentinvention will become apparent from the subsequent detailed descriptionof the invention and the appended claims, taken in conjunction with theaccompanying drawings and this background of the invention.

BRIEF SUMMARY OF THE INVENTION

A method for manufacturing a dye scavenging substrate which comprisesthe steps of: providing an absorbent substrate; passing the substratethrough a bath containing an alkaline solution of a dye scavengingcompound selected from: a N-trisubstitutedammonium-2-hydroxy-3-halopropyl compound having the general formula (I):

wherein R¹, R², R³ are each independently methyl, ethyl, butyl, benzylor an hydroxyl substituted derivative thereof, X′ is a halogen atom, andY′⁻ is chloride, bromide, sulfate or sulfonate; or a salt of epoxypropyl ammonium having the general formula (II):

wherein R⁴, R⁵, R⁶ and Y″⁻ have the same meaning as R², R³ and Y′⁻,respectively, as defined above, or a combination thereof; subjecting thesubstrate to a pressure of from about 0.04 MPa to about 0.40 MPa;wrapping the substrate in a water impermeable material and rotating thesubstrate for a period of from about 12 hours to about 60 hours;removing the water impermeable material and passing the substratethrough a bath containing an acid solution; subjecting the substrate toa pressure of from about 0.15 MPa to about 0.40 MPa; and drying thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and

FIG. 1 is a schematic view of a first part of an apparatus for use inthe method according to the invention;

FIG. 2 is a schematic view of a second part of the apparatus shown inFIG. 1; and

FIG. 3 shows the results of a comparative test carried out toinvestigate the dye pick-up performance of a dye scavenging substrateprepared in accordance with the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of the invention is merely exemplaryin nature and is not intended to limit the invention or the applicationand uses of the invention. Furthermore, there is no intention to bebound by any theory presented in the preceding background of theinvention or the following detailed description of the invention.

The invention provides a method for manufacturing a dye scavengingsubstrate which comprises the steps of:

(a) providing an absorbent substrate;

(b) passing the substrate through a bath containing an alkaline solutionof a dye scavenging compound selected from:

(i) a N-trisubstituted ammonium-2-hydroxy-3-halopropyl compound havingthe general formula (I)

wherein R¹, R², R³ are each independently methyl, ethyl, butyl, benzylor an hydroxyl substituted derivative thereof, X′ is a halogen atom, andY′⁻ is chloride, bromide, sulfate or sulfonate;or(ii) a salt of epoxy propyl ammonium having the general formula (II)

wherein R⁴, R⁵, R⁶ and Y″⁻ have the same meaning as R², R³ and Y′⁻,respectively, as defined above, or a combination thereof;(c) subjecting the substrate to a pressure of from about 0.04 MPa toabout 0.40 MPa;(d) wrapping the substrate in a water impermeable material and rotatingthe substrate for a period of from about 12 hours to about 60 hours;(e) removing the water impermeable material and passing the substratethrough a bath containing an acid solution;(f) subjecting the substrate to a pressure of from about 0.15 MPa toabout 0.40 MPa; and(g) drying the substrate.

Preferably, in step (b), the alkaline solution comprises a basicsolution comprising water and a base, preferably NaOH. Preferably, thebasic solution comprises water and the base in a respective ratio byweight of from about 10:90 to about 50:50, preferably from about 20:80to about 40:60, more preferably about 30:70. Most preferably, the basicsolution is a 30% solution of NaOH available under the trade nameCaustic Soda Liquor from Micro-Bio (Ireland) Ltd, Industrial Estate,Fermoy, County Cork, Ireland.

The compound is preferably a salt of epoxy propyl ammonium having thegeneral formula (II), preferably glycidyltrimethylammonium chloride,also known as (2,3-epoxypropyl)trimethylammonium chloride, available insolid form or as a 72% aqueous solution from Sigma Aldrich, wherein R⁴,R⁵, R⁶ are each methyl and Y″⁻ is chloride.

The alkaline solution preferably comprises the compound and the basicsolution in a respective ratio by weight of from about 1:0.42 to about1:0.83, preferably from about 1:0.56 to about 1:0.69, more preferablyabout 1:0.59. It will be appreciated that these ratios preferably referto the compound in solid form. Optionally, when the compound is providedas a 72% solution, the alkaline solution preferably comprises thecompound and the basic solution in a respective ratio by weight of about1:0.42.

Alternatively, the compound may be a compound of formula (I), forexample 3-chloro-2-hydroxypropyltrimethylammonium chloride, availablefrom Sigma Aldrich, wherein R¹, R², R³ are each methyl, X′ is chlorine,and Y′⁻ is chloride.

Preferably, the alkaline solution is at a temperature of from about 10°C. to about 30° C., more preferably about 20° C.

Preferably, in step (c), the pressure is from about 0.05 MPa to about0.35 MPa, more preferably from about 0.10 MPa to about 0.30 MPa, evenmore preferably from about 0.10 MPa to about 0.25 MPa, still morepreferably from about 0.10 MPa to about 0.20 MPa, even more preferablyfrom about 0.12 MPa to about 0.18 MPa, still more preferably about 0.13MPa or about 0.14 MPa or about 0.15 MPa or about 0.16 MPa or about 0.17MPa, most preferably about 0.16 MPa.

Preferably, in step (c), the pressure is obtained by passing thesubstrate between a pair of rollers, optionally pneumatically actuatedrollers. The rollers are preferably nitrile rubber 70 shore hardnesstype rollers available from Downey Textile Machinery, Spurn Point,Manchester Road, Linthwaite, Huddersfield, West Yorkshire HD7 5RF,United Kingdom. It will, however, be appreciated that any other suitabletype of rollers may be used. Step (c) may be carried out on a textilepadder, e.g. a textile padder available from Downey Textile Machinery,details provided above, but it will be appreciated that step (c) is notlimited to use with this particular apparatus.

Preferably, in step (c), the substrate is passed through the rollers ata speed of from about 10 m.min⁻¹ to about 60 m.min⁻¹, preferably fromabout 20 m.min⁻¹ to about 60 m.min⁻¹, more preferably from about 30m.min⁻¹ to about 60 m.min⁻¹, even more preferably from about 40 m.min⁻¹to about 60 m.min⁻¹, still more preferably from about 50 m.min⁻¹ toabout 60 m.min⁻¹, especially about 55 m.min⁻¹.

Preferably, in step (c), an air manifold is used to maintain constantand consistent air pressure across the substrate, to enable thesubstrate to pick up a consistent weight of the alkaline solutioncontaining the dye scavenging compound, therefore enabling the substrateto demonstrate a consistent and repeatable dye scavenging performance.It will be appreciated that any suitable conventional air manifold maybe used. The air manifold may be provided as part of the textile padder.However, it will be appreciated that the invention is not limitedthereto.

Preferably, in step (d), the substrate is rotated for a period of fromabout 24 hours to about 60 hours, more preferably from about 24 hours toabout 48 hours, still more preferably from about 30 hours to about 48hours, even more preferably from about 36 hours to about 48 hours, evenmore preferably from about 42 hours to about 48 hours, still morepreferably about 43 or 44 or 45 or 46 or 47 or 48 hours, most preferablyabout 48 hours. This step of rotating the substrate is also known as thecuring step.

Preferably, in step (d), the substrate is rotated continuously on aroller. Preferably, in step (d), the temperature (ambient temperature)is from about 10° C. to about 100° C., more preferably from about 10° C.to about 50° C., more preferably from about 10° C. to about 40° C., evenmore preferably from about 10° C. to about 30° C., still more preferablyfrom about 15° C. to about 25° C., even more preferably about 20° C.

Preferably, in step (e), the acid solution comprises water and ahydrochloric acid (HCl) solution, preferably a 11.6 M HCl solution. Theacid solution preferably has a pH from about 1.5 to about 2.5, morepreferably a pH of 2.1. Preferably, a pH probe is placed in the bathcontaining the acid solution in order to maintain the pH at 2.1. Thus,the pH probe conveniently signals the water requirement and this isdosed when required to give the correct pH automatically.

Preferably, the acid solution is at a temperature of from about 10° C.to about 30° C., more preferably about 20° C.

Preferably, in step (f), the pressure is from about 0.20 MPa to about0.35 MPa, still more preferably from about 0.25 MPa to about 0.35 MPa,even more preferably from about 0.28 MPa to about 0.33 MPa, still morepreferably about 0.29 MPa or about 0.30 MPa or about 0.31 MPa or about0.32 MPa, most preferably about 0.30 MPa.

Preferably, in step (f), the pressure is obtained by passing thesubstrate between a pair of rollers, optionally pneumatically actuatedrollers. The rollers are preferably nitrile rubber 70 shore hardnesstype rollers available from Downey Textile Machinery, details providedabove. It will, however, be appreciated that any other suitable type ofrollers may be used. Step (f) may be carried out on a textile padder,e.g. a textile padder available from Downey Textile Machinery, detailsprovided above, but it will be appreciated that step (f) is not limitedto use with this particular apparatus.

Preferably, in step (f), the substrate is passed through the rollers ata speed of from about 10 m.min⁻¹ to about 60 m.min⁻¹, preferably fromabout 20 m.min⁻¹ to about 60 m.min⁻¹, more preferably from about 30m.min⁻¹ to about 60 m.min⁻¹, even more preferably from about 40 m.min⁻¹to about 60 m.min⁻¹, still more preferably from about 50 m.min⁻¹ toabout 60 m.min⁻¹, especially about 55 m.min⁻¹.

Preferably, in step (f), an air manifold is used to maintain constantand consistent air pressure across the substrate, to enable a consistentamount of liquid (neutralizing acid solution) to be squeezed from thesubstrate, thereby enabling the substrate to demonstrate a consistentand repeatable performance. It will be appreciated that any suitableconventional air manifold may be used. The air manifold may be providedas part of the textile padder. However, it will be appreciated that theinvention is not limited thereto.

Without limiting the invention thereto, the minimum pressure in step (f)is preferably higher than the minimum pressure in step (c), as in step(c), it is desirable to retain liquid (the alkaline solution containingthe dye scavenging compound), to allow the liquid to react on thesubstrate, whereas in step (f), it is desirable to remove the liquid(the acid solution used to neutralize the alkaline solution containingthe dye scavenging compound), prior to drying the substrate.

Preferably, in step (g), the drying temperature is from about 95° C. toabout 125° C., preferably from about 100° C. to about 120° C., mostpreferably about 115° C. Optionally, in step (g), the substrate is driedby passing the substrate along one or more drying cylinders, whichdrying cylinders are optionally at a temperature of from about 95° C. toabout 125° C., preferably from about 100° C. to about 120° C., mostpreferably about 115° C. The drying cylinders may be drying cylinderssold under the trade name Prichard available from Downey TextileMachinery, details provided above, but it will be appreciated that theinvention is not limited thereto.

Optionally, after step (f) and prior to step (g), the method maycomprise one or more of the additional steps of (f)(i)-(f)(iv):

-   (f)(i) passing the substrate through a first fresh water rinse;-   (f)(ii) subjecting the substrate to a pressure of from about 0.10    MPa to about 0.30 MPa;-   (f)(iii) passing the substrate through a second fresh water rinse;    and-   (f)(iv) subjecting the substrate to a pressure of from about 0.10    MPa to about 0.30 MPa.

Thus, in one aspect, the method may comprise all steps (a)-(f),(f)(i)-(f)(iv), and (g).

Preferably, in steps (f)(i) and (f)(iii), when present, the first andsecond fresh water rinses take the form of a bath containing water,optionally at a temperature of from about 10° C. to about 30° C.,preferably about 20° C.

Preferably, in steps (f)(ii) and (f)(iv), when present, the pressure isobtained by passing the substrate between a pair of rollers, optionallypneumatically actuated rollers. Details of suitable rollers are providedabove, but it will be appreciated that the invention is not limitedthereto. Preferably, the pressure is approximately 0.2 MPa. Thesubstrate is preferably passed through the rollers at a speed of fromabout 10 m.min⁻¹ to about 60 m.min⁻¹, preferably from about 20 m.min⁻¹to about 60 m.min⁻¹, more preferably from about 30 m.min⁻¹ to about 60m.min⁻¹, even more preferably from about 40 m.min⁻¹ to about 60 m.min⁻¹,still more preferably from about 50 m.min⁻¹ to about 60 m.min⁻¹,especially about 55 m.min⁻¹.

The absorbent substrate may be formed from any suitable material, andmay be woven or non-woven. Examples of suitable materials includecellulosic materials such as viscose, cotton, wood pulp, paper, andmixtures thereof. The material may comprise a naturally occurringmaterial or a synthetic material or a mixture thereof. In an embodiment,the substrate may comprise a blend of viscose and cotton in a ratio byweight in the range of from about 70:30 to about 30:70, optionally fromabout 60:40 to about 40:60, further optionally about 50:50. Theabsorbent substrate may comprise a binder such as polyvinylacetate. Asuitable substrate may be a substrate comprising viscose and cotton in a50:50 ratio by weight, and optionally including a binder, as disclosedfor example in International PCT Patent Publication No. WO-A-97/48789.However, it will be appreciated by a skilled person that the substrateis not limited to being made from the above-listed materials, and bemade from any other suitable material(s), cellulosic or otherwise.

The dye scavenging compound (I) and/or (II) is preferably present in anamount of from about 4.4 g to about 5.5 g, more preferably from about4.6 g to about 5.1 g, most preferably about 4.9 g per square meter ofabsorbent substrate.

The dimensions of the substrate, once cut for use in a domestic wash,are approximately 25 cm×12 cm. It will, however, be appreciated that anyother suitable dimensions may be used. The amount of dye scavengingcompound (I) and/or (II) provided on a 25 cm×12 cm substrate ispreferably from about 0.13 g to about 0.17 g, more preferably from about0.133 g to about 0.16 g, even more preferably from about 0.138 g toabout 0.153 g, most preferably about 0.150 g.

The absorbent substrate material preferably has a weight of from about40 g/m² to 200 g/m², more preferably from about 55 g/m² to 80 g/m², mostpreferably approximately 60 g/m² or 70 g/m².

The rollers used in the method of the invention are preferably nitrilerubber 70 shore hardness type rollers available from Downey TextileMachinery, details provided above.

Advantages of the invention include the following, but are not limitedthereto:

-   -   It has surprisingly been found that using reduced pressure in        step (c) and increased curing (rotation) time in step (d),        compared with the pressure (0.69 MPa to 1.37 MPa) and curing        time (1 hour to 12 hours) disclosed in International PCT Patent        Publication No. WO-A-97/48789, results in a dye scavenging        substrate which performs significantly better in terms of dye        pick-up. Accordingly, it is proposed that the inventors have        surprisingly discovered an optimum pressure and curing time that        provides the resultant dye scavenging substrate with improved        dye pick-up results while also maintaining good tensile        strength.    -   It will be appreciated by a skilled person that only the        pressure range in step (c) and curing time in step (d) are        essential to achieve the improved results. Without wishing to be        bound by theory, it is proposed that the pressure in step (c) is        essential as it allows a sufficient amount of the dye scavenging        compound (provided in the alkaline solution) to be retained on        the substrate; and the curing time in step (d) is essential as        it allows sufficient time for the dye scavenging compound to        react with the substrate to produce superior dye scavenging        results, without allowing the tensile strength to be affected.    -   It will be appreciated by a skilled person that the method of        the invention is not limited to use with a cellulosic substrate,        and that any other suitable absorbent substrate may be used in        order to show the improvement in dye scavenging capabilities        achieved using the method of the invention.

The invention will now be described in greater detail, with reference tothe accompanying non-limiting examples and drawings, in which:

FIG. 1 is a schematic view of a first part of an apparatus for use inthe method according to the invention;

FIG. 2 a schematic view of a second part of the apparatus shown in FIG.1; and

FIG. 3 shows the results of a comparative test carried out toinvestigate the dye pick-up performance of a dye scavenging substrateprepared in accordance with the method of the invention.

Referring now to FIG. 1, there is shown a first part of an apparatus 10for use in the method of the invention which comprises a bath 11containing rollers 12, 20, a pair of pneumatically operated rollers 13,14, and a series of rollers 16.

The method is generally carried out as follows. A roll of absorbentsubstrate 15 is loaded onto a roller bar (not shown) of the first partof the apparatus 10. The substrate 15 is then fed via roller 20 into thebath 11 so as to pass beneath the roller 12 and out of the bath 11 tobetween the rollers 13, 14. By means of pump 30, the bath 11 is chargedwith a basic solution as described above, via line 32. By means of pump31, the bath 11 is charged with a dye scavenging compound solution asdescribed above, via line 33. The rollers 13, 14 are set to provide apressure of from about 0.04 MPa to about 0.40 MPa.

The substrate 15 then passes along the series of rollers 16 along aconvoluted pathway to finally emerge therefrom to be taken up by atake-up roller (not shown) so as to provide a partially treatedsubstrate roll 15′.

The partially treated substrate roll 15′ is then removed from theapparatus 10, wrapped in a water impermeable material, replaced on thetake-up roller, and rotated continuously on the take-up roller at atemperature of from about 10° C. to about 100° C. for a period of fromabout 12 hours to about 60 hours. This step of rotating the partiallytreated substrate roll 15′ is referred to as the curing step. The waterimpermeable material may be a water impermeable film, for examplederived from regenerated cellulose, such as Cellophane (trade mark), forexample Cellophane available from Innovia Films Ltd, Wigton, Cumbria,United Kingdom.

Referring now to FIG. 2, there is shown a second part of the apparatus10, in which like components have been accorded like reference numeralsand unless otherwise stated perform a like function to the componentsshown in FIG. 1.

Once the curing step is complete, the partially treated substrate roll15′ is unwound from the take-up roller onto a roller bar (not shown) andthen onto the roller 20′ of the second part of the apparatus 10. Thesubstrate 15′ is fed via roller 20′ into the bath 11′ so as to passbeneath the roller 12′, and out of the bath 11′ to between thepneumatically operated rollers 13′, 14′. The bath 11′ is charged with anacid solution as described above, by means of a pump (not shown) via aline (not shown). The substrate 15′ then passes along the series ofrollers 16′ and drying cylinders 22 along a convoluted pathway tofinally emerge therefrom to be taken up by a take-up roller (not shown)to provide a treated substrate roll 15″, being the dye scavengingsubstrate. The drying cylinders 22 are preferably at a temperature offrom about 95° C. to about 125° C., to facilitate drying of the treatedsubstrate 15″. The thus produced substrate 15″ is now stored and cutinto appropriately sized pieces, preferably 25 cm×12 cm.

The substrate is preferably passed through the first and second parts ofthe apparatus 10 at a speed of from about 10 m.min⁻¹ to about 60m.min⁻¹.

It will be appreciated that the second part of the apparatus 10 may beadapted to include a series of two baths containing water so as toprovide first and second fresh water rinses. The one or more baths wouldbe provided as part of the apparatus 10 after the bath 11′ and beforethe rollers 16′, so that the substrate 15′ on leaving the bath 11′ wouldpass between the rollers 13′, 14′ and then into a first bath containingwater (not shown), out of the first bath and between a first set ofpneumatically operated rollers (not shown), then into a second bathcontaining water (not shown), out of the second bath and between asecond set of pneumatically actuated rollers (not shown). In thisvariation, the substrate would then pass along the series of rollers 16′and drying cylinders 22 along the convoluted pathway to finally emergeand be taken up by the take-up roller (not shown) to provide a treatedsubstrate roll 15″, being the dye scavenging substrate. It will beappreciated by a skilled person that the fresh water rinses do notaffect the resultant substrate in any substantial way, but serve toremove the odor of the dye scavenging compound.

The method may be carried out on any textile padder, for example atextile padder available from Downey Textile Machinery, details providedabove, but it will be appreciated that the method of the invention isnot limited to use with this particular apparatus.

Example 1

A dye scavenging substrate was prepared as follows. A roll of cellulosicsubstrate 15 was loaded onto a roller bar (not shown) of the first partof the apparatus 10 (FIG. 1), and fed via roller 20 into the bath 11, ata speed of 55 m.min⁻¹. The bath 11 contained an alkaline solutioncomprising a 30% solution of NaOH available under the trade name CausticSoda Liquor from Micro-Bio (Ireland) Ltd, and(2,3-epoxypropyl)trimethylammonium chloride (72% solution) availablefrom Sigma Aldrich, in a respective ratio by weight of 0.42:1. Thealkaline solution was at a temperature of 20° C. The substrate 15 waspassed beneath the roller 12 in the bath, then out of the bath 11 andbetween the pair of pneumatically actuated rollers 13, 14 set to providea pressure of 0.16 MPa. The substrate 15 was then passed along theseries of rollers 16 along a convoluted pathway to finally emergetherefrom and be taken up by a take-up roller (not shown) so as toprovide a partially treated substrate roll 15′. The partially treatedsubstrate roll 15′ was removed from the apparatus 10, wrapped inCellophane (trade mark), replaced on the take-up roller, and rotatedcontinuously on the take-up roller at a temperature of about 20° C. fora period of 48 hours (the curing step). After 48 hours, the substrate15′ was loaded onto a roller bar (not shown) of the second part of theapparatus 10 (FIG. 2), and fed via roller 20′ into the bath 11′, at aspeed of 55 m.min⁻¹. The bath 11′ contained an acid solution comprisinga solution of 11.6 M HCl with water to give a pH of 2.1. The acidsolution was at a temperature of 20° C. The substrate 15′ was passedbeneath the roller 12′ in the bath 11′, then out of the bath 11′ andbetween the pair of pneumatically actuated rollers 13′, 14′ set toprovide a pressure of 0.30 MPa. The substrate 15′ was then passedthrough the series of rollers 16′ and drying cylinders 22, operating ata temperature of 115° C. The substrate 15′ was then taken up by atake-up roller (not shown) to provide the treated substrate roll 15″,being the dye scavenging substrate. The thus produced substrate 15″ wasthen stored and cut into pieces measuring 25 cm×12 cm, and bearing about0.15 g of dye scavenging compound per cut substrate.

The method described in this example was carried out using a textilepadder available from Downey Textile Machinery, details provided above.However, it will be appreciated that the invention is not limited to usewith this particular apparatus.

Example 2

The following comparative test was performed in order to investigate thedye pick-up performance of a dye scavenging substrate prepared inaccordance with the method of the invention.

A solution of dye in water having a dye concentration of 0.100 g/L wasprepared. The performance of substrates prepared in accordance withdifferent methods, including the method of the invention, wasinvestigated. The substrates used were as follows.

X. Substrate (25 cm×12 cm) prepared in accordance with the invention inExample 1 above, i.e. using a pressure in step (c) of 0.16 MPa (“newpressure”) and rotated (cured) for 48 hours.

A. Substrate (25 cm×12 cm) prepared using a pressure in step (c) of 1.03MPa (pressure according to WO 97/48789, “old pressure”) and rotated(cured) for 1 hour, i.e. a difference in pressure and curing time.

B. Substrate (25 cm×12 cm) prepared using a pressure in step (c) of 0.16MPa (“new pressure”) and rotated (cured) for 1 hour, i.e. a differencein curing time.

C. Substrate (25 cm×12 cm) prepared using a pressure in step (c) of 1.03MPa (pressure according to WO 97/48789, “old pressure”) and rotated(cured) for 48 hours, i.e. a difference in pressure.

Substrate X was placed in the dye solution for a period of 3 minutes,following which the substrate was removed and the dye concentration wasmeasured using a spectrophotometer DR3900 available from Hach,Willstatterstr. 11, D-40549 Dusseldorf, Germany. The process was thenrepeated separately for each of the remaining substrates A, B and C,using a fresh dye solution having a dye concentration of 0.100 g/L foreach test. These tests were repeated three times and averages taken. Theresults are shown in Table 1 and in FIG. 3.

TABLE 1 Dye solution before test A B C X Pressure — “Old “New “Old “Newpressure” pressure” pressure” pressure” 1.03 MPa 0.16 MPa 1.03 MPa 0.16MPa Curing Time — 1 hour 1 hour 48 hours 48 hours (rotation ofsubstrate) Remaining dye 0.100 0.064 0.060 0.038 0.022 (g/L) after 3 mintest

Referring to Table 1, the lower the resultant dye concentration after 3minutes, the better the result, as the lower value indicates that thesubstrate in question had scavenged more dye from the dye solution whichis indicative of its effectiveness at picking up loose dye in a laundrywash. It is clear from the results shown in Table 1 that substrate X,prepared in accordance with the invention in Example 1, displayed farsuperior dye pick-up results compared with the substrate A, prepared inusing the pressure (1.03 MPa) and curing time (1 hour) of the prior art(disclosed e.g. in the Example of International PCT Patent PublicationNo. WO-A-97/48789). Substrate X also displayed far superior dye pick-upresults compared with substrates B and C in which only one of pressureor curing time was adjusted compared to the prior art (disclosed in e.g.the Example of WO-A-97/48789). Without wishing to be bound by theory, itis proposed that a surprising synergy is achieved by the reducedpressure and increased curing time used in the method of the presentinvention, thereby producing an unexpected technical effect ofsignificantly improved dye pick-up.

Example 3

The following comparative test was performed in order to investigate thetensile strength of a dye scavenging substrate prepared in accordancewith the method of the invention.

All of the substrates in this Example were prepared using a pressure of0.16 MPa in step (c) (“new pressure”), and varied only in the curingtimes as indicated. The substrates investigated were as follows:

B. Substrate (25 cm×12 cm) was the same Substrate B as tested in Example2 above, i.e. rotated (cured) for 1 hour.

D. Substrate (25 cm×12 cm) was rotated (cured) for 12 hours.

E. Substrate (25 cm×12 cm) was rotated (cured) for 24 hours.

X. Substrate (25 cm×12 cm) was the same Substrate X as tested in Example2 above, i.e. rotated (cured) for 48 hours.

F. Substrate (25 cm×12 cm) was rotated (cured) for 72 hours.

G. Substrate (25 cm×12 cm) was rotated (cured) for 96 hours.

The wet tensile strength of each of the dye scavenging substrates B, D,E, X, F and G was measured as follows. The prepared substrates weresubmerged in a container of water in order to wet the substrates. Oncewet, the wet cross direction (CD) tensile strength of each substrate wasmeasured using a tensile tester A700980 available from Zwick Roell,Southern Avenue, Leominster, Herefordshire HR6 OQH, United Kingdom. Theresults are shown in Table 2.

TABLE 2 B D E X F G Pressure New New New New New New Curing Time 1 h 12h 24 h 48 h 72 h 96 h Wet CD Tensile Strength 542.9 452.3 426.6 415.7399.3 378 (N/m)

Referring to Table 2, the lower the value of the wet cross direction(CD) tensile strength, the weaker the substrate. It will be apparent toa skilled person that a value of wet cross direction tensile strength ofless than 400 N/m would result in a weak substrate which would besusceptible to tearing and disintegrating in a laundry wash, which isundesirable. Accordingly, it is clear from the results shown in Table 2that substrate X, prepared in accordance with the invention in Example1, maintained good tensile strength while exhibiting superior dyepick-up abilities as described in Example 2 above. Indeed all of thesubstrates D, E and X, prepared by a method according to the inventionincluding a curing time of from 12 to 48 hours, all displayed goodtensile strength. It will be appreciated from Table 2 that, although nottested, a substrate prepared by a method according to the inventionincluding a curing time of 60 hours, would also display good tensilestrength.

Accordingly, the method of the invention produces a dye scavengingsubstrate that displays a superior performance in terms of dye pick-up,and yet still maintains good tensile strength in the wash, and issuitable for use in domestic and commercial laundry environments.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention, it being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims and their legal equivalents.

What is claimed is:
 1. A method for manufacturing a dye scavengingsubstrate which comprises the steps of: (a) providing an absorbentsubstrate; (b) passing the substrate through a bath containing analkaline solution of a dye scavenging compound selected from: (i) aN-trisubstituted ammonium-2-hydroxy-3-halopropyl compound having thegeneral formula (I):

wherein R¹, R², R³ are each independently methyl, ethyl, butyl, benzylor an hydroxyl substituted derivative thereof, X′ is a halogen atom, andY′⁻ is chloride, bromide, sulfate or sulfonate; or (ii) a salt of epoxypropyl ammonium having the general formula (II):

wherein R⁴, R⁵, R⁶ and Y″⁻ have the same meaning as R², R³ and Y′⁻,respectively, as defined above, or (iii) a combination thereof; (c)subjecting the substrate to a pressure of from about 0.04 MPa to about0.40 MPa; (d) wrapping the substrate in a water impermeable material androtating the substrate for a period of from about 24 hours to about 60hours; (e) removing the water impermeable material and passing thesubstrate through a bath containing an acid solution; (f) subjecting thesubstrate to a pressure of from about 0.15 MPa to about 0.40 MPa; and(g) drying the substrate.
 2. A method according to claim 1, wherein instep (c), the pressure is from about 0.05 MPa to about 0.35 MPa.
 3. Amethod according to claim 1, wherein in step (c), the pressure isobtained by passing the substrate between a pair of rollers.
 4. A methodaccording to claim 3, wherein in step (c), the substrate is passedthrough the rollers at a speed of from about 10 m.min⁻¹ to about 60m.min⁻¹.
 5. A method according to claim 1, wherein in step (d), thesubstrate is rotated for a period of from about 24 hours to about 48hours.
 6. A method according to claim 1, wherein in step (d), thetemperature is from about 10° C. to about 100° C.
 7. A method accordingto claim 1, wherein in step (b), the alkaline solution is at atemperature of from about 10° C. to about 30° C.
 8. A method accordingto claim 1, wherein in step (e), the acid solution comprises water and ahydrochloric acid (HCl) solution.
 9. A method according to claim 1,wherein in step (f), the pressure is from about 0.20 MPa to about 0.35MPa.
 10. A method according to claim 1 wherein in step (f), the pressureis obtained by passing the substrate between a pair of rollers.
 11. Amethod according to claim 10, wherein in step (f), the substrate ispassed through the rollers at a speed of from about 10 m.min⁻¹ to about60 m.min⁻¹.
 12. A method according to claim 1, wherein in step (g), thedrying temperature is from about 95° C. to about 125° C.
 13. A methodaccording to claim 1, wherein in step (b), the compound isglycidyltrimethylammonium chloride.
 14. A method according to claim 1,wherein the absorbent substrate is a cellulosic material.
 15. A methodaccording to claim 14, wherein the absorbent substrate comprises a blendof viscose and cotton.